Multiple doctor coating process and apparatus



Sept 1, 197G KEIZQ TAKAHAsHl ETAL 3,526,528

MULTIPLE DOCTOR COATING PROCESS AND APPARATUS Filed Oct. 27, 1966 I INVENTORS KEIZO KAHASHI MAMO ISHIWATA BY l ,2; 4 an ATTORNEY$ United States Patent 3,526,528 MULTIPLE DOCTOR COATING PROCESS AND APPARATUS Keizo Takahashi and Mamoru Ishiwata, Kanagawa, Japan,

assignors to Fuji Shashin Film Kabushiki Kaisha, Ashigara-Kamigun, Kanagawa, Japan Filed Oct. 27, 1966, Ser. No. 589,896 Claims priority, application Japan, Oct. 28, 1965, 40/ 66,282; Dec. 15, 1965, 40/76,868 Int. Cl. B44d 1/00 US. Cl. 117-34 8 Claims ABSTRACT OF THE DISCLOSURE A coating apparatus is provided which includes a plurality of separately closed chambers, each having a discharge opening separated from each other by partitions, the ends of which are formed as doctor blades.

The process for coating a plurality of layers on a traveling web includes supplying fluid compositions to each of said chambers, applying said compositions successively to the web and metering the coatings by means of the doctor blades.

The present invention relates to a process and apparatus for applying successively two or more fluid coating compositions to the surface of a continuously travelling web in multiple layers without setting or drying said coated layers between the applications of the coating compositions.

In particular, the process and apparatus of the present invention are suitable for applying at a high speed, in one step, two or more fluid coating compositions, such as photographic, light-sensitive, gelatino silver halide emulsions, to a travelling support, such as, a film base or a baryta paper in thin layers.

That is, according to the present invention the process for coating a plurality of layers on a web comprises providing, in close proximity to the surface of the continuously travelling web to be coated, a coating means having a plurality of separately closed chambers within said coating means, one for each fluid coating composition, and a plurality of discharge openings, separated from each other by partitions formed on doctor blades and each connected to a chamber such that said openings are positioned slightly apart from the surface of said Web, supplying each fluid coating composition into each chamber in an amount corresponding to the pre-determined thickness of coating, applying successively said coating compositions from the openings of the coating means without forming spaces between the coating compositions discharged from said openings while filling the space between the surface of the web and the coating means with the continuously discharged coating compositions to form superimposed, multiple layers of the fluid coating com position between them, metering each of said fluid coating compositions from the coating means on the travelling support to form superimposed and distinct layers on the support. The present invention is also directed to the apparatus described above in conjunction with the process.

Further, according to another embodiment of the present invention, in the multiple coating apparatus as described above, a comparatively wide opening is provided for the first coating layer in the advancing direction of said support as compared with the other openings for the coating compositions.

The present invention will be more clearly understood from the following description when read in connection with the accompanying drawings, in which;

Patented Sept. 1, 1970 FIG. 1 is a cross-sectional view showing a web coating apparatus employed for carrying out an embodiment of the present invention,

FIG. 2 is enlarged cross-sectional view of a part of the web coating apparatus shown in FIG. 1 showing the manner in which a plurality of superimposed and distinct layers are formed in a space defined by the coating apparatus and the support, and

FIG. 3 is a cross-sectional view showing a web coating apparatus employed for carrying out other embodiments of the present invention.

Referring now to FIGS. 1 to 3, there are shown the manners by which the process of the present invention is carried out and the apparatus therefore. In the accompanying drawings, a support web 1 to be coated, such as, a film base or a baryta paper is moved continuously over a roll 2 by any suitable means (not shown). Slightly apart from the surface of said support is positioned a coating means or head 3 having formed therein four chambers 4, 5, 6, and 7 containing coating compositions for forming the first layer, second layer, third layer and fourth layer, respectively, on the support and each chamber is connected to a means for supplying the coating composition in a pre-determined amount. Said coating means 3 also has at the end thereof four openings 8, 9, 10*, and 11 connected to the chambers 4, 5, 6, and 7, respectively, for discharging the coating compositions from the chambers onto the travelling support to provide the multiple layers of the coating compositions. As clearly shown in MG. 2, the openings of the coating means are positioned within a short distance from the surface of the support and they are separated from each other by partitions or end faces of walls 13, 14, and 15. The walls 13, 14, and 15 form slot-like passageways together with walls 12 and 16 for passing the fluid coating compositions in the chambers to the openings.

The walls 13, 14, 15 and 16 are each formed as and act as doctor blades with the end surface of each doctor blade being disposed substantially parallel to the surface of the traveling support web. The ends of each wall or doctor blade as well as the end of the wall 12 are spaced substantially equidistant from the surface of the traveling web as is clearly shown in FIGS. 1 and 2.

When fluid coating compositions, such as, gelatino silver halide emulsions for photography, are applied to the surface of traveling support, such as, a cellulose acetate film or a baryta paper, through the openings 8, 9, 10, and 11, while supplying the coating compositions into the chambers 4, S, 6, and 7, the coating compositions fill the space between the end of each doctor blade of the coating means 3 and are metered onto the surface of the support forming superimposed and distinct layers and the thus formed layers of the fluid coating compositions are continuously withdrawn by the travelling support to form the distinct superimposed multiple layers thereon.

The coating process according to this invention possesses the following desirable attributes;

(1) A plurality of fluid coating compositions can be applied at a stroke without the necessity of allowing the first applied layer to set or dry in advance of applying the second fluid composition to be subsequently coated thereon, which makes it especially possible to increase the production rate to a great extent in the case where the formation of multi-coating layers is required as in a photographic color material.

(2) Since a plurality of fluid coating compositions flow successively in a stratified layer system and always fill the narrow space between the coating means and the surface of the support over a considerable length thereof in a direction in which the support travels, the bridge of 3 coatings formed between the coating means and the support is rarely broken, even if the support travels at a high Speed.

(3) The fluid coating compositions are successively and continuously formed into multiple layers without the formation of air spaces between the end of each blade of the coating means and the surface of a support or between the thus formed layers of the fluid coating compositions, while filling said space with the fluid coating compositions, which results in making it possible to provide each fluid coating composition in the form of a thin layer.

(4) Since the fluid coating compositions discharged from the openings are supplied in superimposed layers between the coating means and the travelling support without forming any air spaces between the layers, a good wetting property is obtained between the layers, which facilitate the selection of surface active agents and the like to be incorporated in the coating composition.

Further, since the thickness of each layer is not substantially determined only by the distance between the surface of a support and the end of a partition wall facing saidsupport surface, as in the usual doctor coating method, but is determined by the factors, such as, the discharging amount of each coating composition, the viscosity thereof, the pressure thereof and the like in the doctor coating process of the present invention, the thickness of each layer can be controlled over a considerably wide range.

The present process also reduces the formation of stripes or commets on the surface of the coated layer as frequently are formed in the case of applying coating compositions onto a support successively with air spaces between the coatings or layers.

In another embodiment of the present invention as shown in FIG. 3, the opening 8 of the coating means for providing the first layer of the fluid coating composition on the travelling support is widened, that is, the clearance of the opening 8 in the travelling direction of the support is increased as compared with those of other openings 9, 10, and 11. In the case shown in FIG. 1 or FIG. 2, the clearances of the openings are preferably shorter than 3 mm. but in the case shown in FIG. 3, the clearance of the opening 8 is longer than 3 mm. and those of the openings 9, 10, and 11, the clearances of which are also shorter than 3 mm.

The use of such a system as shown in FIG. 3 provides a further advantage. That is, since the opening for discharging the fluid coating composition for the first layer is widened and, hence, the fluid coating composition is contacted with the surface of the travelling support in a comparatively wide area, the bridge of the coating composition bet-ween the coating means and the support does not tend to be broken and the entrance of air between the support and the coating layer can be prevented, which results in increasing the coating speed.

EXAMPLE Four kinds of fluid coating compositions for a positive cine color film were applied at one stroke to the surface of a cellulose triacetate film, having an undercoat or substratum, by means of the coating apparatus as shown in FIGS. 1 and 3 in accordance with the present inven tion. The conditions were as follows:

Feeding ra (liter/mirn/ layer.

The dimension of the space between the end of the coating means and the surface of the film was about 0.2-0.5 mm. and the travelling speed of the film was 30 meter/min.

Upon inspection of the cine color film obtained by allowing the thus coated layers to set rapidly after the completion of coating under the conditions mentioned above and to dry, there were observed neither unevenness in thickness of the coated layers not defects over all the surface area of the coating, and, further, no intermixing of coating compositions was observed between the coated layers. Thus, the product was considered to have a satisfactory quality.

While the invention has been explained with reference to certain specific embodiments, it should clearly be understood by those skilled in the art that many changes or modifications may be possible, and the invention shall not be limited to the precise details concerning the kind of a coating composition and the construction of a coating apparatus.

What is claimed is:

1. A process for coating multiple, distinct layers on a web backed by a suitable surface and travelling at a high rate of speed comprising locating adjacent to said web a coating head having only a plurality of discharge openings directed toward said web, a plurality of chambers each connected to a respective discharge opening with a doctor blade forming a downstream portion of each discharge opening in the direction of travel of said web and located in close proximity to said web, supplying fluid coating compositions into each of said chambers, applying said coating compositions successively to the surface of said web from said discharge openings without forming spaces between said coatings while filling the space between the surface of the web and said doctor blades with said coating compositions, maintaining said coating compositions between said web and said doctor blades under pressure and metering said coating compositions by means of said doctor blades to form superimposed and distinct multiple layers of said fluid coating compositions on said web.

2. The multiple coating process as claimed in claim 1 wherein said coating compositions are gelatino silver halide emulsions, an emulsion for protective layer, an emulsion for antihalation layer, an emulsion for filter layer, or an emulsion for masking layer.

3. A multiple doctor coating apparatus for successively applying a plurality of coating compositions to the surface of a web travelling over a back-up surface comprising:

(a) a coating head having a plurality of chambers each adapted to receive a coating composition from a suitable supply means;

(h) each of said chambers having a discharge opening, said openings being successively adjacent to each other in the direction of travel of said web, with a doctor blade forming a downstream portion of each discharge opening in the direction of travel of said web and located in close proximity to said web;

(0) said doctor blades having an end surface facing said web substantially parallel thereto and spaced substantially equally distant therefrom, said doctor blades acting to meter each of said coating compositions as said coating compositions are discharged from their respective opening into the space between said doctor blades and the surface of said web.

4. A multiple doctor coating apparatus as set forth in claim 3 wherein the width of each of said discharge openings in the direction of travel of said web is substantially equal for all openings.

5. A multiple doctor coating apparatus as set forth in claim 3 wherein the width of each of said discharge openings in the direction of travel of said web is not greater than three mm.

5 6 6. A multiple doctor coating apparatus as set forth References Cited in claim 3 wherein said end surfaces of said doctor blades UNITED STATES PATENTS have a substantial width in the direction of travel of said web. 2,761,791 4/1956 Russell 11734 7. A multiple doctor coating apparatus as set forth 5 g gg t in claim 3 wherein the Width of the first discharge opening in the direction of travel of said web is substantially ALFRED L LEAVITT, Primary Examiner 2:111:51 than the width of the remaining discharge open- J. A. BELL, Assistant Examiner 8. A multiple doctor coating apparatus as set forth in 10 US Cl. XR.

claim 7 wherein the Width of the remaining discharge openings is not greater than 3 mm. 1 18-15; 117-459 813 118-410 411 

